JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div id="parent">
<div><p>A</p></div>
<div><p>B</p></div>
    </div>
</body>

CSS

#parent
{
    width:200px;
    height:200px;
}
#parent div:nth-child(1){
    background-color: blue; 
    border-bottom: 10px solid black;
    margin-bottom: 20px;
  }
#parent div:nth-child(2){
    background-color: green; 
    border-top: 10px solid yellow;
  }